Design of multi-epitope chimeric phage nanocarrier vaccines for porcine deltacoronavirus

Porcine delta coronavirus (PDCoV) poses a significant threat to the swine industry. Thus, the development of innovative vaccine candidates is critical for PDCoV prevention. This study details the creation of a PDCoV nanoparticle vaccine utilizing bacteriophage (phage) T4 as a delivery platform. B cell and T cell epitopes of the PDCoV spike (S) protein were identified through bioinformatics and assembled into a tandem construct (termed Pep) using a linker. In silico molecular docking revealed stable interactions between Pep and TLR3. Immune stimulation predictions indicated that Pep could trigger a robust immune response. The prokaryotic Pep protein was conjugated with T4 phage to generate the recombinant T4-Pep phage. Experimental data demonstrated that a single T4 phage displayed at least 830 copies of Pep. In a mouse immunoprotection assay, T4-Pep induced significantly higher levels of specific IgG antibodies and superior neutralizing antibody titers against PDCoV compared to the Pep naked peptide antigen. Moreover, T4 phage exhibited potent immunostimulatory effects, with immunized mice showing protection against PDCoV infection. Histological analysis revealed enhanced intestinal mucosal integrity post-immunization. These findings suggest that bacteriophages are promising vectors for the efficient delivery of viral epitopes, offering a potential platform for developing vaccines against porcine enteric coronaviruses.